LeAnn Rimes is grateful for so many things—but she has had her share of struggles.

And she still wishes that she had done a few things differently when she met husband Eddie Cibrian on the set of the Lifetime movie Northern Lights in 2009, when both of them were married to other people.

"I don't like the word regret," she says in a sit-down with Giuliana Rancic for E! Special: LeAnn Rimes, airing Sunday at 8 p.m. "I wish I handled it differently because I wish I could have been better for me, for Brandi [Glanville, Cibrian's ex-wife], for Dean [Sheremet, her ex-husband], for Eddie, for everyone else.

"I know, in this situation, it's going to take some time. All I wish is that everyone that was hurt, that we hurt, that I hurt, can be happy."

Rimes also talks to Rancic about the 30-day treatment program she completed earlier this year, telling her of that tumultuous time, "When you look around and you go 'I'm crying, like, uncontrollably, no one can help me,' that's when I knew I had to seek help...I was incredibly depressed and not quite sure of who I was."

"People are so quick to judge and make decisions for themselves about situations they know absolutely nothing about," she says, noting how quick people were to speculate the worst about what was troubling her.

"My heart goes out to her every single time she's getting bashed for something," the actor tells E!. "It's unfair for her and it's unfair for us. [The affair] wasn't frivolous, you know."

"No one will ever understand how much thought and hurt were put into our decision" to end their respective marriages, says Rimes, who filed for divorce from Sheremet after seven years together in December 2009.